Dave Dombrowski was dismissed because of his actions leading up to the 2015 non-waiver trade deadline.
Dombrowski was not under contract beyond 2015 and on the surface, it appeared it was a mutual parting between him and the organization he has helped reach the postseason in five out nine seasons since 2006. But according to Lynn Henning of The Detroit News, Tigers Owner Mike IIitch was not pleased when Dombrowski suggested the Tigers do not have the trade pieces necessary to acquire a starting pitcher before the deadline.
Henning adds that instead of recommending trading for another top arm or additional bat, Dombrowski made it clear the organization should "exploit a historically high July market." Dombrowski wanted to deal players who would be classified as rentals for top minor league talent with the goal of ensuring long-term stability in Detroit.
By the time the deadline had passed, the Tigers had sent David Price to Toronto, Yoenis Cespedes to New York, and Joakim Soria to Pittsburgh. The return was six prospects, five of which were pitchers. Dombrowski had accomplished exactly what he wanted to, adding minor league depth in exchange for impending free agents, however according to Henning, IIitch was not pleased with the situation.
Once IIitch agreed to look beyond 2015, Henning adds, Dombrowski knew his job might be on the line:
The quasi-surrender of 2015, even if based on reality and a club’s future health, is understood to have sealed his exit.
Dombrowski was reportedly not given an explanation for IIitch's decision and was told that it was a "change of direction." However, based on the circumstances and last minute notice Dombrowski received, it appears to have been a firing and not a mutual parting of ways.
Either IIitch knew he was going to replace Dombrowsi and let him make deals leading up to the deadline anyway or IIitch made a quick and recent decision. The reports do not align, however, since Avila was told he would become the next Tigers General Manager on Saturday and Dombrowski was not aware he was being dismissed until Monday or Tuesday.
IIitch did sign off on the moves Dombrowski made leading up to the trade deadline. But he likely did not agree with them and they might have ultimately cost Dombrowski his job.